A liquid crystal display (LCD) device is a flat panel display device that includes a liquid crystal layer sandwiched between two substrates, where one of the substrates can be an active device substrate that has an array of active devices (e.g., thin film transistors or TFTs) to control application of electric fields in corresponding pixel areas of the LCD device.
In conventional LCD devices, light leakage may occur at storage capacitors (Cst) in the pixel areas. FIG. 1 is a schematic view of a pixel structure P1 in a pixel area of a conventional LCD device. The pixel structure P1 includes a substrate 100, a data line 102, a scan line 104, a pixel electrode 106, a common line 108, and an active device (e.g., TFT) T1 disposed on the substrate 100. The common line 108 has a capacitor portion 108a and a connector portion 108b, and the active device T1 is electrically connected to the scan line 102 and the data line 104. The scan line 102 controls activation/deactivation of the active device T1, and the data line 104 provides a data voltage that is to be applied to the pixel electrode 106 when the corresponding active device T1 is activated. The pixel electrode 106 is electrically connected to the active device T1 and covers the capacitor portion 108a, and the overlapped part of the pixel electrode 106 and the capacitor portion 108a forms a storage capacitor (Cst). To enhance the storage capacity of the storage capacitor, a capacitor electrode 110 is provided above the capacitor portion 108a of the common line 108. The capacitor electrode 110 is disposed between the pixel electrode 106 and the capacitor portion 108a, and is electrically connected to the pixel electrode 106. In addition, an alignment layer (not shown) is also disposed on the substrate 100 and covers the aforementioned elements. In FIG. 1, Dc1 represents a direction in which the capacitor portion 108a extends, and Da1 represents an alignment direction of the alignment layer.
Since there are more film layers in a region (e.g., region A10) of the substrate 100 where the common line 108 is located than in other regions, the alignment layer covering the substrate 100 will have a portion in the region A10 that protrudes higher than the remaining portions of the alignment layer on the two sides of region A10 defined by the common line 108, which can cause a fringe field in the region A10. As a result, liquid crystal molecules in the region A10 may be oriented in an incorrect manner, different from the orientation of liquid crystal molecules in other regions of the same pixel region, thereby causing light leakage in the region A10. As a result, the display contrast may be reduced, thereby causing a poor display effect of the LCD device.